DOMESTIC HOT WATER CONSUMPTION AND ITS IMPACT ON SYSTEMS WITH CIRCULATION: Analyzing variations in use of domestic hot water in a student accommodation building and investigations on the resulting performance of hot water systems with circulation

DOMESTIC HOT WATER CONSUMPTION AND ITS IMPACT ON SYSTEMS WITH CIRCULATION

Apostolov, Dimitar ; Burnazov, Plamen Tsvetanov

4. Term

Building Energy Design

2017

2017-01-13

98

This thesis examines how domestic hot water (DHW) usage patterns influence the performance of circulation-based systems in a student residence. Using four years of daily metered data from a 99-apartment building in Aarhus, the study analyzes monthly, seasonal, and weekday–weekend variations and develops representative yearly profiles. These data underpin a benchmark simulation of the building’s DHW system to identify common inefficiencies and to compare the circulation solution with alternatives such as storage tank and electric heat-tracing systems. Findings show stable average daily consumption across years, lower use in summer (with frequent zero-use days in July) and peaks in February, and more frequent small daily draw volumes in summer. Weekday use is up to 8% higher than weekends, but the difference is minor when days without use are excluded. Simulations indicate that the placement of the temperature sensor controlling circulation affects tap temperatures, can trigger circulation during draw-offs, and may raise primary-side return temperatures, reducing efficiency. Tapping frequency and volume also influence circulation behavior and delivered temperature. Alternative systems can outperform circulation in some applications, but the optimal design is highly case dependent. The analysis is limited by the capabilities of the chosen software, and further work with more advanced tools is recommended.

Denne afhandling undersøger, hvordan brugsmønstre for varmt brugsvand påvirker ydeevnen af systemer med cirkulation i en kollegiebolig. Med fire års daglige målinger fra en bygning med 99 lejligheder i Aarhus analyseres månedlige, sæsonmæssige og hverdag–weekend-variationer, og der udarbejdes repræsentative årlige profiler. Disse data bruges til at opbygge en referencesimulationsmodel af bygningens varmtvandsanlæg for at identificere typiske ineffektiviteter og sammenligne et cirkulationssystem med alternativer som lagertank og el-tracing. Resultaterne viser stabilt gennemsnitligt dagligt forbrug på tværs af årene, lavere forbrug om sommeren (med hyppige nulforbrugsdage i juli) og toppunkter i februar; mindre daglige tappevolumener forekommer oftere om sommeren. Forbruget på hverdage er op til 8 % højere end i weekender, men forskellen er lille, når dage uden forbrug udelades. Simulationerne indikerer, at placeringen af temperaturføleren, der styrer cirkulationen, påvirker taptemperaturer, kan udløse cirkulation under tapping og øge returtemperaturen på primærsiden, hvilket reducerer effektiviteten. Tappefrekvens og -volumen påvirker ligeledes cirkulationen og den leverede temperatur. Alternative systemer kan i visse tilfælde yde bedre end cirkulation, men den optimale løsning er stærkt sagsafhængig. Analysen er begrænset af den anvendte softwares muligheder, og der anbefales opfølgende studier med mere avancerede værktøjer.

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